I noticed it too. It happens when I click on a link that is designated with the domain name instead of the IP address, and when I log in it doesn't take me to the link location, instead to the main page.
I believe it is due to the Domain Name in the link which hasn't fully resolved yet for the cookies to work properly. Or it could be a cookie issue dealing with the domain name.
Just some information, I am confident Veks will figure this one out also.